GREEN SYNTHESIS OF SILVER NANOPARTICLES
USING POLYSACCHARIDE EXTRACTED FROM
LAURENCIA OBTUSA ALGAE
Magdy K. Zahran and Hana A. Mohammed
Chemistry Department, Faculty of Science, Helwan University, Ain-Helwan,
Cairo,11795, Egypt.
Key Words: silver nanopartecles, polysaccharide, L. obtusa, FT-IR,
XRD and TEM
ABSTRACT
The aim of this work was to synthesis of silver nanoparticles
(AgNPs) using water soluble Polysaccharide extracted from marine algae
(L. obtusa) as reducing agents for silver ions as well as stabilizing agents
for the synthesized AgNPs. The formation of silver nanoparticles was
confirmed by Surface Plasmon Resonance (SPR) at 350 to 550 mm, by
using fourier transform infrared spectroscopy (FT-IR), X-ray diffraction
(XRD) and transmission electron microscopy (TEM). The maximum
absorption peaks are in the range of 400-420 nm. The particles were
spherical in shape in the range of 4-10 nm.
1. INTRODUCTION
Many researchers have widely used noble nanoparticles in various
technological applications because of their unique properties. The noble
metal nanoparticles, in general, and silver nanoparticles (AgNPs), in
particular, are known for their versatile applications in medical [Becker,
1999], food processing [Tankhiwale and Bajpai, 2010] and textile
industries [Duran et al., 2010] as well as in consumer goods [Jiang et
al., 2004; Rai et al., 2009].
A large number of physical, chemical, biological, and hybrid
methods are available to synthesize different types of nanoparticles [Liu
et al., 2001]. The nanoparticles formed using each method show specific
properties. However, biosynthesis of metal nanoparticles by plant
extracts is a green modern alternative for their production [Shameli et
al., 2012]. Green synthesis of nanoparticles makes use of
environmentally friendly, non-toxic and safe reagents [Salam et al.,
2012].
The main objectives of the present study are: (i) to synthesize
AgNPs using polysaccharide of L. obtusa algae (ii) to characterize
AgNPs using UV–Vis spectroscopy, FT-IR, XRD and TEM.
2. EXPERIMENTAL
2.1. Material
The red algal used throughout the present work were collected from
the beach of Red Sea, Alexandria, Egypt. These were found attached to
Egypt. J. of Appl. Sci., 36 (1) 2021 9-16
the rocky belt existed about 15 meters from the sea-shore and at about
two meters depth and were Freshly collected algal species were
repeatedly washed with sea-water followed by tap-water to remove sand,
salt and any extraneous matters. The cleaned samples were shade dried
and homogenized to fine powder and kept for further treatments.
2.2. Extraction of polysaccharide
The defatted algae powder was successively percolated with hot
water till complete exhaustion. The extract was concentrated to about 50
ml under reduced pressure using rotary evaporator device. Polysaccharide
were precipitated using Absolute ethanol (250 ml) which added dropwise
with stirring till complete precipitation occurred. The residue
obtained was washed with absolute ethanol then weighed and saved for
further study.
2.3. Synthesis of silver nanoparticles (AgNPs)
AgNPs were synthesized from silver nitrate using polysaccharide
of L. obtusa as reducing and stabilizing agent. 30 mg of the extract
residue dissolve 95 ml of distilled water and adjust pH =12 using sodium
Hydroxide and complete volume to 99 ml with distilled water then put it
on magnetic stirrer hot plate at temperature 90 °C and added 1ml of
(0.1M) AgNO3 solution were added to the reaction mixture then the
reaction mixture was kept at different durations (15, 30, 45, and 60min).
2.3.1. Ultraviolet-visible (UV-vis) spectroscopy analysis
Change in color was visually observed in the silver nitrate solution
incubated with polysaccharide of L. obtusa. The reduction of silver ions
was monitored from 300 to 800 nm by Jasco V-670 UV-V after 5-fold
diluting the sample with distilled water against distilled extract as blank
at a resolution of 1 nm.
2.3.2. Fourier transform infrared (FTIR) spectroscopy analysis
For FTIR spectroscopy measurements, the bio-synthesized
AgNPs were purified, dried and palleted with potassium bromide in
the ratio of 1:100. FTIR spectrum of samples was recorded on
(JASCO FT-IR 4100 instrument, Japan). All measurements were
carried out in the range of 400– 4000 cm-1 at a resolution of 4 cm-1.
2.3.3. Transmission electron microscopy (TEM).
The size and morphology of the synthesized AgNPs were
determined by high resolution transmission electron microscopy
(TEM, JEOL JEM 2100, Japan). The sample for TEM studies was
prepared as follows: 1 ml of the reaction mixture containing
AgNPs was diluted to 5 ml, sonicated using ultrasonic bath and a
10 Egypt. J. of Appl. Sci., 36 (1) 2021
drop of it was placed on a Cu grid with ultrathin Cu on holey Cfilm
and it was allowed to dry in a vacuum. The instrument was
operated with an acceleration voltage of 200 kV.
2.3.4. X-ray diffraction (XRD)
The synthesized nanoparticles were examined by XRD (6000 -
shimadzu - Japan). The powdered AgNPs was stacked in the cubes of
XRD and the result was taken in the XRD equipment at this condition:
X-ray tube target, copper potassium alpha radiation; voltage, 40.0 (kV);
current, 30.0 (mA). Divergence slit, 1.00000 (deg); scatter slit, 0.00000
(deg); receiving slit, 0.30000(mm). Scanning drive axis, Theta-2Theta,
scan range, 4.0000 - 90.0000 (deg); scan mode, continuous scan; scan
speed, 8.0000 (deg/min); sampling pitch, 0.0200 (deg).
3. RESULTS AND DISCUSSION
3.1. Visible observation
The Colour of L. obtusa Polysaccharide before addition of
AgNO3 solution is yellow, after its treatment with AgNO3
solution, the colour changes to reddish-brown which indicated the
formation of AgNPs (Fig. 1). This colour change is due to
surface Plasmon excitation of the formed nanoparticles which
affects the optical property.
Figure 1: Colour change before and after addition of AgNO3 solution.
Where (A) the polysaccharide of L. obtusa algae (B) the
biosynthesized AgNPs
3.2. UV-vis spectra analysis
UV-Vis absorption spectroscopy is an important technique to
determine the formation and stabilization of biosynthesized AgNPs
in aqueous solution. AgNPs were synthesized at optimized
Egypt. J. of Appl. Sci., 36 (1) 2021 11
conditions of temperature 90°C and pH=12 meanwhile the time was
varied (15, 30, 45 and 60 min), the formation of silver nanoparticles
was monitored by UV spectrophotometer. The maximum absorption
peaks are in the range of 400-420 nm which is a typical plasmon
band of silver metal [Durán et al., 2005; Ahmad et al., 2003],
suggesting the formation of silver nanoparticles (Fig. 2).
Figure 2: UV-Visible absorption spectra of biosynthesized silver
nanoparticles from polysaccharide extract of L. obtusa at
different times interval, constant pH and temperature.
3.3. FTIR spectroscopy
FTIR study reveals the multi-functionality of L. obtusa
polysaccharide by identifying the possible functional groups in the
biomolecules of this poly saccharides. A FT-IR spectrum of the
synthesized AgNPs and polysaccharide by this green method is
shown in Figure 3. Data of this figure indicate that the
polysaccharide manifest absorption peaks at about 3441 were
assigned to OH stretching vibration, the peak at 2932 cm-1
corresponds to C-H alkane ,1480 represent –C=C– group. The peak
at 1141 cm-1 corresponds to C-O stretching vibration. These results
were previously proved by Parida et al., 2014; Namvar et al., 2014.
As is evident (Fig. 3), both FTIR spectra of the Polysaccharide
extract and the Polysaccharide extract containing AgNPs have the
same trend but the intensity of functional groups present in
nanoparticlrs sample is small, and this proves that the different
functional groups in the bioactive compounds polyphenols, protein
and polysaccharide are consumed for reduction of Ag+ to Ag0 and
stabilization of the biosynthesized AgNPs.
12 Egypt. J. of Appl. Sci., 36 (1) 2021
Figure 3. FTIR spectra of (A) Polysaccharide extract of L. obtusa algae and (B)
biosynthesized AgNPs
3.4. Transmission Electron Microscope (TEM)
TEM provides further insight into the morphology and particle size
distribution profile of the AgNPs and revealed a pattern similar to that of
the biosynthesized AgNPs characterized by TEM [Bindhu and Umadevi,
2013; Das et al., 2013]. The data obtained from transmission electronmicrograph
(Fig. 4) showed distinct shape and size of AgNPs. The
particles were spherical in shape in the range of 5-10 nm.
Figure 4. TEM of AgNPs from polysaccharide of L. obtusa algae.
Egypt. J. of Appl. Sci., 36 (1) 2021 13
3.5. XRD analysis
Analysis through X-ray diffraction was carried out to confirm the
crystalline nature of the particles, and the XRD pattern showed numbers
of Braggs reflections that may be indexed on the basis of the face
centered cubic (fcc) structure of silver. A comparison of our XRD
spectrum with the standard confirmed that the silver particles formed in
our experiments were in the form of nanocrystals, as evidenced by the
peaks at 2θ values of 38, 44.7, and 65, and 77.7 θ, corresponding to
(111), (200), (220) and (311), respectively Bragg reflections of silver.
The XRD results clearly show that the silver nanoparticles formed by the
reduction of Ag+ ions by the L. obtusa polysaccharide are crystalline in
nature [Umoren et al., 2014].
Figure 5 . XRD pattern of AgNPs from Polysaccharide of L. obtusa algae .
4. CONCLUSION
Green chemistry approach towards the synthesis of nanoparticles has
many advantages such as, ease with which the process can be scaled up and
economic viability. We have developed a fast, eco-friendly and convenient
method for the synthesis of silver nanoparticles using L. obtusa
polysaccharide with a diameter range of size 5-10 nm. These particles and
spherical. No chemical reagent or surfactant template was required in this
method, which consequently enables the bioprocess with the advantage of
being environmentally friendly. Color change occurs due to surface plasmon
resonance (SPR) during the reaction with the ingredients present in the
polysaccharide extract results in the formation of silver nanoparticles which
is confirmed by UV–Vis, FT-IR, TEM and XRD.
14 Egypt. J. of Appl. Sci., 36 (1) 2021
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التحضير الآخضر لجسيمات الفضة النانو مترية باستخدام السکريات العديدة
المستخمصة من طحمب لو ا رنسيا اوبتيو ا ز
مجدي قنديل زه ا رن 1 ، هناء عمي محمد 2
-1 أستاذ الکيمياء العضوية – کمية العموم – جامعة حموان
-2 باحث – قسم الکيمياء– کمية العموم – جامعة حموان
تيدف ىذه الد ا رسة الي تحضير جسيمات فضة نانومتريو وذلک باستخدام السکريات
العديدة المستخمصة من الطحالب البحرية کعوامل مختزلو لأيون الفضة کما استخدمت في نفس
الوقت ايضا کعوامل مثبتو لجسيمات الفضة النانوية التي تم تحضيرىا. وقد تم التأکد من تکوين
جزيئات الفضة النانو مترية عن طريق بعض التحاليل الطيفية باستخدام مطياف الأشعة فوق
833 نانومتر، مطياف الاشعة - عند طول موجي من 333 (UV-vis.) البنفسجية-المرئية
والميکروسکوب (XRD) وطاقة التشتت لطيف الاشعة السينية (FTIR) تحت الحم ا رء
- وقد أظيرت ىذه الجسيمات أقصى قمة امتصاص عند 433 - (TEM) الالکتروني النافذ
13 نانومتر. - 423 نانومتر وکانت دائرية الشکل ويت ا روح حجميا من 4
16 Egypt. J. of Appl. Sci., 36 (1) 2021
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